This invention relates to cables produced using polyvinylidene fluoride and/or their copolymers (“PVDF”) capable of meeting the limited combustible requirements as defined in standard NFPA 90A (Standard for the Installation of Air Conditioning and Ventilation Systems), which Standard requires that such cables when tested by standard NFPA-259 have a potential heat value (“PHV”) below 3500 BTU/pound and when tested by NFPA-255 have a smoke developed index (“SDI”) below 50 and a flame developed index (“FDI”) below 25. Such limited combustible cables (“LC Cables”) are also referred to in industry as Duct Cables, CMD, 25/50/8, 25/50, CMP-50 Cables and/or by other references indicating compliance with the PHV, SDI and FDI requirements referenced in the NFPA 90A Standard for limited combustible materials.
To date, all LC Cables have been developed with fluorinated ethylene propylene (“FEP”) resins for both their primary insulation and jacket components. Applicant is not aware of any LC Cables made commercially using PVDF in one or more of the components. In order to meet the ever more stringent standards for these products, it would be useful to find alternative resins which can provide improved properties. PVDF has historically been limited to applications where its poor dielectric properties do not interfere with the performance of a cable.
It has been understood in industry that PVDF compounds with high limited oxygen index (“LOI”) values would be useful for plenum grade cables. Such high LOI compositions are taught, for example, by U.S. Pat. Nos. 4,898,906 and 5,919,852. The present invention has found that these earlier teachings are not applicable to LC Cables.